However, the Iranian dictator reiterated his warnings against what he termed US "deceit," underlining how the regime in Tehran still remains decidedly hostile towards America.

"I reiterate the need to be vigilant about the deceit and treachery of arrogant countries, especially the United States, in this (nuclear) issue and other issues," Khamenei said, in comments carried by Reuters.

"Be careful that the other side fully meets its commitments. The comments made by some American politicians in last two, three days are suspicious," he continued, likely referring to critical remarks by Republican presidential candidates, some of whom have threatened to walk about on the deal after Obama leaves office next year.

Khamenei – who wields ultimate authority in the Islamic Republic – also sent a letter of congratulations to President Hassan Rouhani, who spearheaded the initiative to reach a deal with the P5+1 powers.

While Rouhani and his Foreign Minister Javad Zarif have been the visible figureheads of the Iranian negotiation efforts, Khamenei has played something of a double game, quietly approving of the talks while making regular aggressive statements about the US and its allies.

Rouhani is planning a trip to Europe in the aftermath of the deal's initial implementation, where businesses are already lining up to cash in on lucrative deals following the lifting of economic sanctions on Iran.